The objective is to establish that biosynthesis of poly(adenosine diphosphate ribose) participates in oocyte maturation. The Xenopus oocyte as a model for this study offers certain advantages. The large size of the oocytes allows substances to be administered by microinjection under physiological conditions. In addition, the oocyte possesses a prominent nucleus, the germinal vesicle (G.V.) which offers a unique opportunity to study nuclear events during maturation, e.g., chromosome condensation. Under progesterone treatment, the oocyte undergoes an orderly sequence of events that will permit a detailed dissection of the events associated with meiosis, especially the biochemical sequence from meiotic prophase to maturation accompanied by G.V. breakdown. Morphological observations on oocyte during its maturation suggest that mitochondria participate in the meiotic process. This notion is based on the findings that a large part of the oocyte DNA is located in the mitochondria; that the mitochondria migrates and concentrates in the vicinity of the nuclear membrane during maturation; and that the mitochondria intertwines with the nuclear material on disintegration of the nuclear membrane. Although the precise role of the mitochondria in the maturation process is not known, we have demonstrated that oocyte mitochondria, in addition to being a functional unit to promote oxidative phosphorylation, contains an active poly(ADPR) synthase which transfers the ADPR moiety of NAD ion to an acceptor protein(s). It is hypothesized that the acceptor protein(s) in some indeterminate manner participate in the regulation of the maturation process by being transformed from an active to an inactive form by ADP-ribosylation. This hypothesis is supported by our findings as follows: 1) nicotinamide blocks oocyte maturation in several species; 2) nicotinamide is rapidly and almost completely converted to NAD ion in the oocyte; 3) an active poly(ADPR) synthase is located in oocyte mitochondria; 4) NAD ion microinjected into Xenopus oocyte is converted to oligomers of ADPR attached to protein(s). This reaction probably takes place in the mitochondria. By carrying out the planned experiment, the specific aims will be accomplished and those issues will be resolved.